After an all-nighter, Mio's hair was a disaster.
Too large in scale to call bedhead, and a sticky note from yesterday was still stuck to the collar of her lab coat. She didn't care in the slightest. No resources had been allocated anywhere in her brain for caring.
"Oh, come on, Mio!"
Aya yelled it three seconds after walking in. "It's a bird's nest again! Come here a sec. Sit."
Mio obediently sat in a chair. Complying took less time than resisting. Standing behind her, Aya briskly combed her hair and tied it up with a hair tie, peeled off the sticky note, and even brushed away the snack crumbs on the shoulders of her lab coat.
"There. Human again." Aya rested a hand on Mio's shoulder, satisfied. "Make sure you eat properly today, okay? I'm not letting my Mio starve to death. That's my life's mission."
"I can manage my own blood sugar."
"I'm saying it because you can't!" Aya pulled her chair right up next to Mio's, leaned in close as if to link arms, and took a box of chocolates out of her bag. "Look, the limited edition. Let's eat them together."
Mio picked one up. The sweetness soaked into her empty brain. It wasn't bad.
Mikoshiba watched the whole thing from his own desk.
He was pretending to look at the numbers on his tablet, but his gaze had clearly stopped right around where Aya's arm went around Mio's shoulder. He said nothing. He just got up to make coffee—and, for some reason, set the cup he'd made precisely between Mio and Aya.
"Himuro. Sugar alone will dehydrate you. Get some fluids in, too."
Then, with a perfectly natural motion, he wedged a chair in between Mio and Aya.
"The traffic flow is bad," he said. "People pass through here a lot. Aya, move over toward the wall. It's optimizing the... placement of resources."
"The placement of resources," Aya repeated in a monotone. "Huh."
That afternoon, Mio's work efficiency visibly dropped.
Her typos increased, she nearly wrote the same function twice, and once she almost spilled coffee on her keyboard. Each time, Aya came over to fuss over her, rubbing her shoulders, resupplying snacks, rebuttoning Mio's lab coat.
Mikoshiba observed it. And in the evening, standing before the whiteboard with his arms folded, he reached a conclusion.
"I've noticed something," he said. "On days Aya fusses over Himuro, Himuro's bugs increase."
"Huh?" Aya turned around.
"It's data," Mikoshiba went on calmly. "Over the past three days, on days Aya looked after Himuro, test failures at commit time were clearly above average. In other words—Aya's clinging is lowering Himuro's work efficiency. That's a business risk. We need to review our resource allocation."
What it came down to was that he wanted to peel Aya off Mio. But the only things that came out of his mouth, to the very end, were "business risk" and "resource allocation."
Mio looked up from her keyboard. There was a flaw in how Mikoshiba had built his conclusion that she couldn't let pass. She rolled up the sleeves of her lab coat, stood, and took the whiteboard marker out of Mikoshiba's hand. When the subject turned technical, she suddenly became fluent. Her reason for staying passive disappeared.
"Mikoshiba. That conclusion is missing a cross-check." Mio drew two lines on the whiteboard. "What you saw is only the fact that two numbers moved together. From there you jumped to 'Aya's clinging is the cause, and my bugs are the effect.' But the reason two lines move together usually has a much more boring shape."
"A boring shape."
"The shape where both are being pushed from behind by some third thing." Mio added a thick arrow at the roots of the two lines. "Listen. My bugs increase on days after an all-nighter, when my brain is worn out. Once sleep debt passes a certain level, the precision of working memory drops. Typos, errors in judgment—they all come from there."
Mio turned the tip of the arrow toward Mikoshiba.
"And—it's precisely on days when I've pulled an all-nighter and look like a bird's nest that Aya comes to fix my hair. So the true cause is 'the all-nighter.' 'Aya's clinging' and 'my bugs' are both its results. Aya isn't in the cause column. She's an innocent passerby who happened to be in the same place on the same day."
With the butt of the marker, Mio gave the conclusion Mikoshiba had written a light tap.
"You just framed an innocent passerby as the culprit. As ways of misreading data go, it's the most classic inversion there is."
Mikoshiba started to open his mouth. Mio cut him off. The initiative was already entirely on her side.
"Disproving it is simple. If you keep Aya away and I keep pulling all-nighters, the bugs won't go down. Conversely, if Aya keeps clinging and I sleep, the bugs disappear. Which one do you move to change the result? Banning one without testing that is just having the conclusion first and attaching the data afterward. That's not like you."
At that final jab, Mikoshiba went still, just slightly.
It was less a refutation than a dismantling. The "reason to peel Aya off" he had raised was dug up by Mio's own hands, all the way down to the confounding variable at its root, and invalidated. And because Mio had processed it so perfectly as a technical problem—she never once laid a finger on the conclusion's real motive: his unease at the picture of a stunning designer with her arm around a beloved genius. What she had solved was the equation, not Mikoshiba.
"...I see." Mikoshiba looked for a while at the diagram on the whiteboard that Mio had thrust back at him. "I misread the data. I retract it."
He went back to his seat. But the chair that had moved Aya toward the wall, he did not retract.